KR0184687B1 - Solid state imaging device having high sensitivity and exhibiting high degree of light utilization and method of manufacturing the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid state imaging device and a method of manufacturing the same, and more particularly, to a solid state imaging device in which a microlens is formed on a photoelectric conversion portion and a manufacturing method thereof. An insulating film 42, a transfer electrode 43, a light shielding film 44, a protective film 45, and a planarization layer 51 are formed on the photoelectric conversion portion, and the concave lens layer 52 is lattice-shaped on the planarization layer 51. To form. The lattice-shaped concave lens layer 52 is hot melted and converted into a concave micro lens layer. The resin layer 53, the buffer layer 54, and the convex microlens 57, which are lower in refractive index than the concave lens 52, are sequentially formed on the concave lens layer 52. This concave lens layer 52 has a function of causing the light beams collected by the convex microlenses 57 to be incident vertically on the photoelectric conversion section 41.

Description

Solid state imaging device and manufacturing method thereof

1A, b, c, d and e are process drawings for explaining a first embodiment of a method for manufacturing a solid state imaging device according to the present invention.

2 is a perspective view of a lattice pattern resist formed by passing pixel regions therethrough.

3 is a perspective view showing a state in which the resist is hot melted;

4A, 4B and 4C are process drawings for explaining a second embodiment of the method for manufacturing a solid-state imaging device according to the present invention.

5A and 5B are process drawings for explaining a third embodiment of the method for manufacturing a solid-state imaging device according to the present invention.

6a, b and c show a conceptual diagram of a conventional example and a conceptual diagram of the present invention;

7a, b, c and d are process drawings for explaining the fourth embodiment of the method for manufacturing the solid-state imaging device of the present invention.

8A and 8B show a condensing operation of the conventional example.

8C is a view showing a condensing operation of the present invention.

9A and 9B are views for comparing the condensing operation of the conventional example with that of the present invention.

FIG. 10 is a graph showing reflectance dependence on reflectance and incident angle of light incident on a material having a refractive index of 1.6.

* Explanation of symbols for main parts of the drawings

1,41,61,81: photoelectric conversion unit 2,42,82: interlayer insulating film

3,43,83: transfer electrode 4,44,64,84: light shielding film

5,45,85: protective film 16,51,71: planarization layer

17 silicon nitride layer 18 photosensitive resist

19,75: resist layer 52: concave lens layer

53: low refractive index resin layer 54: buffer layer

57: convex microlens 76: concave microlens layer

86170: concave microlens 95: resist

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid state imaging device and a method of manufacturing the same, and more particularly, to a solid state imaging device including a photoelectric conversion unit and a microlens formed on the photoelectric conversion unit and a manufacturing method thereof.

In recent years, in the solid state imaging device technology, the sensitivity has been remarkably improved by using a microlens.

Conventionally, in the solid state imaging device having a microlens, there is a solid state imaging device as shown in Fig. 8A. 8A shows the optical system in the unit pixel of the solid state imaging device. In FIG. 8A, reference numeral 181 denotes a photoelectric conversion portion, 182 denotes an interlayer insulating film, 183 denotes a transfer electrode for signal charge, 184 denotes a light shielding portion over each transfer electrode, and 185 denotes a protective layer, Denoted at 186 is a transparent resin layer or microlens support layer, 187 is a microlens, 188 is vertical incident light to the lens end, and 189 is oblique incident light.

As shown in FIG. 8A, this solid-state imaging device is adapted to guide the vertical incident light 188 to the photoelectric conversion section 181 by the microlens 187 to improve the sensitivity.

8B shows the incident state of light into the photoelectric conversion section of the conventional solid state imaging device. In FIG. 8B, reference numeral 190 denotes an incident light beam at a normal aperture position, 191 is an effective photoelectric conversion region, 192 is an area where photoelectric conversion is actually performed, and 193 is an aperture. When opened, the long-wavelength light 194 reaching the oblique incidence state near the signal charge transmission region is an actual aperture composed of a light shielding film or the like.

Today, solid-state imaging devices have a wide range of uses, from video movies to surveillance cameras and the like. Indeed, solid-state imaging devices have been applied to almost all kinds of optical systems because of their various uses.

In many cases, it has been found that optical changes in the optical system, which have not been treated as a serious problem in the past, such as aperture changes in camera lens optics, have a significant effect on image quality, screen brightness, and the like. In this regard, the conventional solid state imaging device has the following drawbacks.

In such a conventional solid state imaging device, in many cases, the state where the aperture becomes narrower is optimal in the design of the microlens optical system. That is, as shown in FIG. 8A, a design in which the vertical incident light 188 to the lens end is not eroded but incident to the photoelectric conversion portion is considered ideal.

However, when the lens is used in a state almost close to liberation, such as when imaging in a dark room, the ratio of the total incident light amount of the oblique incident light indicated by reference numeral 189 in FIG. 8A increases significantly. As a result, the ratio of the light encroached by the structure around the hole and failing to enter the photoelectric conversion unit 181 increases, thereby substantially decreasing the sensitivity.

If the solid state imaging device is a color imaging device, there is another problem that white balance may be adversely affected.

As described above, in the conventional solid-state imaging device of this type, the image quality may be deteriorated due to the change of the imaging condition.

In the conventional solid-state imaging device, the configuration of the microlens is that, as shown in FIG. 8B, the region 192 through which the incident light beam passes through the photoelectric conversion unit 191 is moved to the vicinity of the center of the photoelectric conversion unit 191. It is limited. Accordingly, the generated carriers are locally close to supersaturation at the center of the photoelectric conversion portion, and the probability of electron transition in this portion is likely to be lowered to the order of carrier diffusion time. The reason can be found basically that the part which is completely depleted has the highest electron transition probability.

In general, the photoelectric conversion unit 191 itself is an N-type layer, and the periphery of the photoelectric conversion unit 191 is surrounded by the P-type layer. Therefore, the peripheral portion of the photoelectric conversion unit 191 has a large potential gradient and a high probability of transition of electrons. However, as already described, the conventional solid-state imaging device has a disadvantage in that such a peripheral portion cannot be used for photoelectric conversion. For this reason, the conventional apparatus is never efficient in terms of sensitivity.

The incident light passing through the microlens may basically be inclined with respect to the photoelectric conversion unit. Therefore, in consideration of the depth (5-10 μm) in which the long wavelength light of the visible region penetrates the substrate including the photoelectric conversion part, the light is transmitted inside the signal charge transmission part adjacent to the photoelectric conversion part or at a portion very close to the signal charge transmission part. There is little probability that photoelectric conversion to incident light will be performed. This is not necessarily good from the standpoint of smear suppression.

Therefore, in order to optimize the imaging conditions, it is necessary to match both the photoelectric conversion region and the microlens optical system.

When considering a single lens, in general, if the diameter of the lens (this diameter is better to consider the diameter of the subject) is constant, the shorter the focal length, the brighter the lens. In other words, using such a lens increases the illuminance of the screen. In short, the larger the curvature of the lens, the higher the device sensitivity. Thus, conventional devices have a relatively large curvature microlens.

However, as the curvature of the microlenses increases, the incident angle of incident light at the point where light enters the lens increases with respect to the contact surface of the lens. At this time, as shown in FIG. 10 showing the reflectance Rs of the s component and the reflectance Rp of the p component with respect to the material having a refractive index of 1.6, when the incident angle θ is 60 degrees or more, the related reflectance is insignificantly high (for example, , In this case Rs = 21%), the reflection of light on the microlens surface is insignificantly high. As a result, the sensitivity is lowered.

As described above, in the conventional apparatus, there is still a problem to be solved with respect to light utilization as described above.

It is therefore an object of the present invention to provide a solid state image pickup device and a method of manufacturing the same, which have high sensitivity and can increase light utilization.

In order to achieve the above object, there is provided a solid-state imaging device having a plurality of pixels including a photoelectric conversion section and convex microlenses disposed on the photoelectric conversion section; A support layer formed between the photoelectric conversion unit and the convex microlens to support the convex microlens; And a concave microlens layer disposed between the support layer and the photoelectric conversion unit and formed of a material having a refractive index higher than that of the material constituting the support layer.

This solid-state imaging device is designed such that the concave microlens layer causes the light beams collected by the convex microlenses to enter the photoelectric conversion unit in parallel to the vertical incident light.

By collimating the collected light rays, it is possible to prevent the collected light from colliding with the aperture surrounding the space facing the photoelectric conversion part on the photoelectric conversion part. Therefore, the sensitivity is improved.

In addition, when the condensed light is parallelized, an area of the light beams formed by the condensed light may be incident on the photoelectric conversion unit. In this case, the effective utilization area of the photoelectric conversion unit is increased, and the sensitivity is improved.

Also provided is a concave lens seating layer disposed between the concave microlens layer and the support layer to support the support layer; The material of the material supporting layer of the concave microlens and the material of the concave microlens layer are both designed to have a higher refractive index than the material of the concave lens attaching layer.

In addition, the solid state image pickup device according to the present invention is designed such that the concave microlens layer is incident on the photoelectric conversion portion by parallelizing the light beams condensed by the convex microlenses.

Since the material of the convex microlens, the material of the support layer, and the material of the concave microlens layer are higher in refractive index than the material of the concave lens attaching layer, the luminous flux collected by the convex microlens is not diffused during concave lens installation. For this reason, the light condensing characteristic is improved.

Since the concave lens attachment layer made of a material having a lower refractive index than the support layer is disposed directly below the support layer, the curvature of the convex microlenses can be made smaller than without the above concave lens attachment layer without increasing the focal length. Therefore, reflection of incident light on the convex microlens surface can be prevented.

A method for manufacturing a solid-state imaging device that sequentially forms a concave microlens layer, a support layer, and a convex microlens on a photoelectric conversion portion, comprising: on the photoelectric conversion portion, a material constituting the convex microlens and a material constituting the support layer. Forming a flat layer of transparent material having a high refractive index; Forming a lattice pattern layer made of a photosensitive resin on the surface of the flat layer and facing the photoelectric conversion unit: heat-melting the lattice pattern layer to concave the lattice pattern layer Converting to a concave microlens pattern layer having a plurality of concave portions of a lens shape; And etching the concave microlens pattern layer to transfer the concave microlens shape of the microlens pattern layer to the flattened layer under the concave microlens layer, thereby converting the flattened layer to the concave microlens layer. Provided is a method of manufacturing a solid state imaging device.

According to the manufacturing method of the solid-state imaging device of the present invention, after forming the concave microlens pattern layer by heat melting the lattice pattern layer, the concave microlens pattern layer is etched to provide the concave microlens layer shape. Transfer to a flat layer for The solid state imaging device of the present disease is manufactured in this way.

A method for manufacturing a solid-state imaging device that sequentially forms a concave microlens layer, a lens mounting layer, and a convex microlens on a photoelectric conversion portion, the method comprising: a photosensitive resin material having a higher light transmittance and a refractive index than a constituent material of the lens mounting layer Forming a lattice pattern layer having through-holes opposite to the photoelectric conversion portion on the photoelectric conversion portion; and heat-treating the hot melted lattice pattern layer after heat melting the lattice pattern layer, A method for manufacturing a solid-state imaging device comprising converting a lattice pattern layer into a concave microlens layer is provided.

According to this method, a solid-state imaging device is manufactured by thermally melting a lattice pattern layer to form a concave microlens layer.

A method for manufacturing a solid-state imaging device, in which a concave microlens layer, a support layer, and a convex microlens are sequentially formed on a photoelectric conversion portion, comprising: patterning and curing a photosensitive resin material in a lattice shape, and through holes facing the photoelectric conversion portion. Forming a lattice pattern layer having a photoresist on the photoelectric conversion unit; and forming an overcoat layer made of a transparent resin on the lattice pattern layer to enable the overcoat layer to act as a concave microlens layer. A method of making a device is provided.

According to this method, the concave microlens layer can be formed without thermal melting the lattice pattern layer. For this reason, the concave micro lens layer with good reproducibility can be formed.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the solid-state imaging device and the manufacturing method of the present invention.

First, in order to compare the present invention with the conventional example, a cross-sectional model of a conventional unit pixel is shown in FIG. 9A, and a representative cross-sectional model of the present invention is shown in FIG. 9B. In the conventional model shown in FIG. 9A and the model of the present invention shown in FIG. 9B, it is assumed that the substantial apertures, holes, and convex microlenses are the same size, respectively. As shown in FIG. 9B, the model of the present invention is uniquely different from the conventional model in that the concave microlens 170 is provided directly under the convex microlens 197.

9A and 9B, reference numerals 198 and 199 denote vertically incident light and obliquely incident light at the microlens end, respectively. The vertical incident light 198 is designed to focus on the surface center portion of the photoelectric conversion region d in the conventional model of FIG. 9A. In contrast, in the model of the present invention of FIG. 9B, the vertical incident light 198 is refracted by the concave micro lens 170 and designed to diffuse widely in the photoelectric conversion region.

In the conventional model of FIG. 9A, the oblique incident light is blocked by the stop 204 and is not incident to the photoelectric conversion unit 207. On the other hand, in the model of the present invention of FIG. 9B, the inclined incident light 199 is refracted by the concave microlens 170 and is incident on the photoelectric conversion section 207.

Compared with the prior art example and this invention based on FIG. 8A, b, and c figure. As shown in FIG. 8A, the geometry of the unit pixels of the solid state image pickup device includes an effective aperture formed of the light shielding film 184 or the electrode 183. As shown in FIG. FIG. 8B shows a conventional configuration corresponding to FIGS. 8A, d and e showing the present invention.

According to the configuration of the present invention in which the concave microlens 205 having a high refractive index is formed directly on the photoelectric conversion section including the effective photoelectric conversion region 201 as shown in FIG. 8C, the upper portion of the concave microlens 205 is upward. The luminous flux 210 is refracted by the concave microlens 205, which is refracted by the convex microlens (not shown) disposed at and started to be focused toward the focal point of the convex microlens, so that the luminous flux 210 is perpendicular. It is almost parallel to the direction. Therefore, according to the present invention, the incident light beams refracted by the convex microlenses in the condensing process are parallelized in the traveling direction by the concave microlenses to convert into almost parallel light beams having substantially the same cross-sectional area as the photoelectric conversion unit. . Therefore, according to the present invention, the ratio occupied by the light beam passing region 202 in the effective photoelectric conversion region 201 is increased as compared with the conventional example. That is, the utilization efficiency of the effective photoelectric conversion region is improved and the sensitivity is improved.

In the solid-state imaging device of the present invention, since the concave microlens is formed under the convex microlens and the support layer of the convex microlens, the concave microlens is formed using a transparent resin material having a higher refractive index than the block microlens and the support layer. Any luminous flux collected through the lens may be parallel light above the photoelectric conversion section.

In the above configuration of the present invention, the support layer of the convex microlenses is made of a transparent resin material having a lower refractive index than the convex microlenses and the concave microlenses. This further improves the parallelism of the rays. In addition, a flat layer made of a transparent resin having a lower refractive index than the convex microlenses and the support layer may be formed as an intermediate layer directly under the support layer.

Example 1

1A and 1B show an embodiment of a method of manufacturing a solid state imaging device according to the present invention. 1 shows the structure of a cell representing the unit pixels of the solid state imaging device.

As shown in FIG. 1A, the transfer electrodes 3 having the interlayer insulating film 2 inserted therein are formed on a substrate including the photoelectric conversion section 1 in a region not facing the photoelectric conversion section 1. After the light shielding film 4 is arrange | positioned so that this transfer electrode 3 may be covered, the protective film 5 which covers both the light shielding film 4 and the photoelectric conversion part 1 is formed. This protective film 5 is for protecting the base monochrome device. Immediately after the protective film 5 is formed, annealing is performed in a hydrogen atmosphere. This annealing is one method of relaxation (relaxation) of the interface level due to lattice mismatch at the interface between the active region of the photoelectric conversion section 1 and the oxide film. The planarization layer 16 is formed on the protective film 5. The planarization layer 16 is made of a hot melt low melting point glass or a spin-on glass (SOG) film and is intended to alleviate all surface steps generated by the electrodes 3 and the like. On the planarization layer 16, a silicon nitride layer 17 having a thickness of about 1.5 mu m of silicon nitride is formed by a chemical vapor deposition method or the like. Although the thickness of the said silicon nitride layer 17 changes with the grade of the said step, it is normally set to 1.5-2.0 micrometers. The refractive index of the silicon nitride layer 17 depends on the growth conditions of the silicon nitride layer 17, but is usually 2.0 or more. The silicon nitride layer 17 is a concave microlens having a high refractive index through the following steps.

Subsequently, as shown in FIG. 1B, the photosensitive resist 18 patterned in a lattice form is formed on the silicon nitride layer 17 by photolithography through which the pixel portion opposite to the photoelectric conversion section 1 is penetrated. Form. This resist is viewed obliquely from above in FIG. 2. This resist 18 is formed of a thermoplastic resin represented by a novolak resin. The resist 18 is melted by heating to a temperature of about 180 ° C., and formed into a resist layer 19 having a concave microlens of the form shown by broken lines in FIG. 1B. 3 is a view of the heat-melting resist layer 19 obliquely from above.

Next, as shown in FIG. 1C, the resist layer 19 is called dry with a fluorine-based gas 20 such as CF ₄ +0 _2, CHF ₃ + O _2, or CHF ₃ + O ₂ . By this dry etching, the concave microlens shape of the resist layer 19 is transferred to the silicon nitride layer 17 under the resist layer 19. Specifically, for example, when plasma-etching SF ₆ with an output of about 200 W, the selectivity is 2: 1 or more, and the final shape of the silicon nitride layer 17 has the concave microlens shape of the resist layer 19 in the longitudinal direction. It becomes the shape extended twice.

In FIG. 1d, the final shape of the silicon nitride layer 17 formed by the concave microlens is shown.

The manufacturing method shown in FIGS. 1A to 1D has high reproducibility and good stability. However, since the planarization layer 16 made of glass having a relatively low refractive index (usually about 1.5) is inserted between the photoresist part 1 and the silicon nitride layer 17 which becomes a concave microlens, this planarization layer There is a possibility that the parallelization performance of the silicon nitride layer 17 which becomes the concave micro lens 16 is somewhat reduced.

Therefore, the silicon nitride layer 17 can be formed directly on the protective film 5 in order to make good use of the step coverage of silicon nitride in vapor phase growth. In this case, a pseudo concave microlens 170 having a thickness of about 2.0 μm can be obtained as shown in FIG. 1E. The concave shape of the concave microlens 170 is emphasized by using the transfer method of FIGS. 1b and c, in which the lattice resist 18 is hot melted and etched, and the shape of the concave microlens 170 is shown in FIG. It is set as the same shape as the concave micro lens of the same favorable shape. The concave microlens 170 can be formed into a concave microlens with good parallelization performance. Thereafter, as shown in FIG. 9B, the surface of the concave microlens 170 is flatly overcoated with a transparent flattening resin layer such as polymethylmetha crylate (PMMA), and convex microlenses (in a conventional manner) on the surface of the flattening resin. 197, to form a solid-state imaging device of the present invention. The transparent flattening resin layer 186 is a support layer that supports the convex microlenses 197. The concave microlenses 170 are formed of a material having a higher refractive index than any of the transparent resin layer 186 and the convex microlenses 197.

This solid-state imaging device uses the concave microlens 170 to parallel the inclined incident light 199 shown in FIG. 9B onto the substantially diaphragm 204 including an electrode, so that the inclined incident light 199 is photoelectric converted. Incident to the unit 207 can be made. Therefore, in the solid state imaging device, the inclined incident light 199 that has been blocked by the aperture 204 and has not been incident to the photoelectric conversion unit 207 can be incident to the photoelectric conversion unit 207. Therefore, according to this solid state imaging device, the sensitivity is improved.

The concave microlens 170 serves to substantially enlarge the image aperture corresponding to the light-receiving side hole of the solid state imaging device in a special optical system such as a microlens of the solid state imaging device.

Conventionally, although the arrangement of the light beam is focused on the surface of the photoelectric conversion portion, the solid-state imaging device of the present invention converts the light flux into parallel light flux having a large incident cross-sectional area in the photoelectric conversion portion 207 as shown in FIG. 9B. can do.

Therefore, in the solid-state imaging device of the present invention, the conventional light beam passing region 192 shown in FIG. 8B can be expanded to the light beam passing region 202 shown in FIG. 8D. As a result, the photon density per unit volume in the beam passing region 202 is lowered. Therefore, as shown in FIG. 8C (C), it is possible to prevent local supersaturation (NsAt) of the generated signal electrons, thereby preventing the temporary decrease in photoelectric saturation rate.

As shown in FIG. 8C, the solid-state imaging device can extend the incident light beam 210 in the transverse direction parallel to the surface of the photoelectric conversion region 201 as compared with the conventional example, and thus has a large unit gradient. Photoelectric conversion can be performed at the peripheral end of the converter, i.e., the complete depletion region with high transition probability. For this reason, photoelectric conversion efficiency improves.

According to the solid state imaging device of this embodiment, as shown in Fig. 8B (B), the inclined incident light 193 of a small angle which may cause smear can be paralleled by the concave microlens 170. have. Therefore, smear reduction can be aimed at.

Example 2

4A to C show a second embodiment of the manufacturing method of the solid-state imaging device of the present invention, and show a concave microlens forming process of the unit pixel cell.

As shown in FIG. 4A, the transfer electrodes 43 having the interlayer insulating film 42 inserted in a region not facing the photoelectric conversion section 41 on the substrate including the photoelectric conversion section 41 are first placed. Form. A light shielding film 44 covering the transmission positive electrode 43 is formed, and a protective film 45 covering the light shielding film 44 and the photoelectric conversion part 41 is formed. Subsequently, in order to reduce the step by the transfer electrode 43 or the like, a planarization layer 51 made of a resin having a high refractive index, such as polystyrene, is formed on the passivation layer 45, and in this planarization layer 51. As a result, the uneven surface is flattened. Next, the concave lens layer 52 is formed. The concave lens layer 52 is a planarization layer 51 using, for example, spin coating or the like of a photosensitive resin based on a thermoplastic resin (threshold temperature 120-180 ° C., refractive index 1.6 or more) such as novolak resin or polystyrene. After coating on it, it is patterned by lithography to form a lattice shape.

The shape of the concave lens layer 52 is generally in the form of a lattice as shown in FIG. 2, but if the penetrating portion is formed in an elliptical shape instead of a rectangular shape, resolution may be facilitated even when these are arranged at a fine pitch. Further, as shown in FIG. 4B, the ideal concave microlens shape can be easily obtained by thermal melting.

Since the thickness of the concave lens layer 52 largely depends on the geometric configuration of the optical system, it can finally be determined based on this geometric configuration. However, from the viewpoint of parallelization performance, the thickness of the concave lens layer 52 is preferably 1 μm or more.

As shown in FIG. 4B, the concave lens layer 52 is thermally melted to form a concave lens shape, and as shown in FIG. 4C, a transparent low refractive index resin layer having a lower refractive index than the concave lens layer on the concave lens layer 52 Alternatively, the planarization layer 53 is formed.

The material of the low refractive index resin layer 53 is considerably limited because a low refractive index is required. The refractive index depends largely on the polarization rate and the molecular weight of the constituent molecules, and the smaller the two are, the better the refractive indexes are. At present, it is known that transparent fluorine resins such as CYTOP of Asai Glass have a low refractive index of about 1.34. However, the fluorine resin is few and oleophobic, and thus the surface energy is relatively low and the adhesion is extremely poor. Therefore, in order to enhance the adhesion, it is preferable to insert the adhesion strengthening thin film composed of a surfactant or the like into close contact with the low refractive index resin layer 53.

On the low refractive index resin layer 53, a buffer layer 54 is formed as a support layer. The buffer layer 54 is a very important layer that serves to improve adhesion to the upper and lower layers and other physicochemical matching. This buffer layer 54 is preferably made of acrylic resin.

Finally, convex microlenses 57 are formed on the buffer layer 54.

In the solid-state imaging device manufactured according to the second embodiment shown in FIG. 4C, since the low refractive index resin layer 53 is provided, the paralleling effect of the concave lens layer 52 can be improved.

Example 3

5A and 5B show a third embodiment of the manufacturing method of the solid state imaging device of the present invention, and show a process of forming a concave microlens of a unit pixel cell. In this embodiment, the steps up to forming the planarization layer 71 having a high refractive index are the same as in the above-described second embodiment, and thus description thereof is omitted.

In the present embodiment, as shown in FIG. 5A, a resist layer 75 having a lattice pattern serving as the foundation of the concave microlens layer is formed on the planarization layer 71. As shown in FIG. The resist layer 75 is patterned with a photosensitive resin, and surrounds the light receiving region facing the photoelectric conversion section 61. Reference numeral 63 is a transfer electrode.

When the resist layer 75 is formed of a material containing a dye that absorbs g-rays or i-rays, it is possible to prevent reflection in the high-reflectance light shielding film 64 during the lithographic process of the microlens forming step, Anti-halation effects can be expected. In the case where the resist layer 75 is formed of a novolac resin, g-ray and i-ray absorption effects are obtained.

Subsequently, as shown in FIG. 5B, a resin having a high refractive index (for example, polystyrene) is coated on the resist layer 75 and the planarization layer 71 by spin coating or the like to form a concave microlens layer 76. The concave microlens layer 76 is an overcoating layer. The formation of the concave microlens layer 76 can be controlled only by adjusting the line width of the resist pattern of the resist layer 75 and the viscosity of the high refractive index resin. In this case, there is an advantage that the concave microlens layer 76 can be formed with relatively good reproducibility.

Then, in the same manner as in the second embodiment, the low refractive index resin layer 53 made of a resin material having a refractive index lower than that of the concave microlens layer 76, the buffer layer 54 and the convex microlens 57 are It forms in order as 5b. The manufacture of the solid state imaging device is thus completed.

Example 4

7 shows a process of forming a concave microlens according to a fourth embodiment of the method of manufacturing a solid-state imaging device of the present invention.

As shown in FIG. 7A, the concave microlens 86 having a high refractive index is formed on the protective film 85 formed on the photoelectric conversion part 81, the transfer electrode 83, the interlayer insulating film 82, and the light shielding film 84. ). On this concave microlens 86, a resist 95 made of the same resin as that of the resist layer 75 of the third embodiment is applied, and the resist 95 is exposed by photolithography to expose the resist 95 as described above. It is formed in a lattice pattern surrounding the hole portion facing the photoelectric conversion section 81.

Subsequently, as shown in FIG. 7A, the resist 95 formed in the lattice pattern is sufficiently cured by heat treatment or the like.

Next, as shown in FIG. 7C, a low refractive index resin (eg, CYTOP) having a lower refractive index than the material of the concave microlens 86 is coated on the surface of the resist 95 and the concave microlens 86. The concave lens attachment layer 100 is formed.

Next, as shown in FIG. 7D, the surface of the concave lens mounting layer 100 is overcoated with a high refractive index resin 101 (for example, polystyrene) of the type used as the overcoating material of the third embodiment. The step of 100 is flattened. Thereafter, a convex microlens 97 having a small percentage of bone is formed on the resin 101.

The concave lens attachment layer 100 is made of a material having a lower refractive index than that of the material constituting the convex microlens 97.

The concept of the condensing operation of the solid-state imaging device manufactured by the fourth embodiment will be described with reference to FIGS. 6A to 6C. FIG. 6A illustrates the condensing operation concept of the conventional example, and FIG. 6B illustrates the condensing operation concept of the first to third embodiments of the present invention, and FIG. 6C illustrates the condensing operation concept of the fourth embodiment of the present invention. .

As shown in FIG. 6A, the conventional art includes a relatively low-convex convex microlens with an edge relief of less than 60 °. The curvature of the convex microlenses and the effective focal length OF1 (distance from point 0 to F1) can take various values in some cases.

An object of the present invention is to overcome the problem that the incident light is disturbed by the substantial cooker 174 including the side wall of the electrode. The basic improvement direction for the problem of disturbing incident light is to focus the incident light in front of the aperture position shown in FIG. 6A in the light traveling direction, and to parallelize the luminous flux of the incident light from the aperture position to the image field.

The microlenses of the solid state imaging device do not belong to the category of so-called imaging optical systems. That is, the microlens of the solid state imaging device is a special optical system installed to guide the radiation flux incident on the surface of the microlens (the amount of the radiation flux in the form of energy) into the photoelectric conversion region without loss.

From the viewpoint of reducing the loss in the process of inducing incident light into the photoelectric conversion section, the conventional art of FIG. 6A has the following three drawbacks (i) to (iii). That is, since (i) the waveguide facility of the light is not established, any oblique incident light is lost by the aperture 174, and (ii) the horizontal magnification of the image closely related to the focal length increases in the long focal length lens system. The image becomes larger than the top aperture, which is quite inefficient at the light collecting surface, which is an important task of microlenses; (iii) When adopting a lens with a large curvature (embossed at an edge portion of the lens of 60 ° or more), reflection of incident light on the lens surface can no longer be ignored.

The crystal (i) can be improved by the first and second embodiments of the present invention, and the defect (ii) can be overcome by increasing the curvature of the convex microlens shown in Fig. 6b.

However, increasing the curvature of the convex microlenses, as shown in FIG. 6B, causes considerable losses due to reflected light on the lens surface, and thus cannot overcome the above defect (iii).

Therefore, in the solid-state imaging device manufactured according to the fourth embodiment shown in FIG. 6C, the concave lens installation layer 100 made of a material having a low refractive index (about 1.3) is made of a material having a high refractive index (about 1.6). Immediately below the convex microlens 97 with a small curvature. The support layer 101 and the convex microlenses 97 together form a convex microlens.

According to FIG. 6C, the radiation flux comparable to FIG. 6B is refracted at the surface of the concave lens installation layer 100, resulting in an optical field in which the virtual focal point F in the absence of the concave microlens 86 is focused on. . That is, in the structure of FIG. 6C, the curvature of the uppermost surface of the convex microlens is smaller than that of FIG. 6B, but has a light converging characteristic optically equivalent to that of FIG. 6B. This is because the angle θ of the peripheral light of FIG. 6C with respect to the virtual focal point F is the same as the angle θ of the peripheral light of FIG. 6B with respect to the virtual focal point F. FIG.

According to the structure of FIG. 6C, the reflection on the surface of the convex microlens can be lowered compared to the structure of FIG. 6B, and the light condensing characteristic equivalent to that of FIG. 6B can be realized.

As will be clear from the above description, the solid-state imaging device of the present invention is formed between the photoelectric conversion unit and the convex microlenses, and is disposed below the support layer and the support layer for supporting the convex microlenses, and the material of the convex microlenses and the support layer. And a concave microlens layer made of a material having a high refractive index.

Therefore, the solid-state imaging device of the present invention is designed such that the concave microlens layer causes light condensed on the convex microlens to be incident to the photoelectric conversion part in parallel parallel to the incident light.

By parallelizing the focused light, the focused light can be prevented from colliding with an aperture surrounding a space facing the photoelectric conversion part on the photoelectric conversion part. This improves the sensitivity.

In addition, when the condensed light is parallelized, an area of the light beam formed by the condensed light may be increased to the light conversion part. In this case, the effective utilization area of the photoelectric conversion unit is increased, and the sensitivity is improved.

In addition, in the solid state image pickup device according to the present invention, the concave microlens layer is designed so that the light beams collected by the convex microlenses are incident in parallel with the vertical incident light onto the photoelectric conversion portion.

Since the refractive index of the material constituting the convex microlens is higher than the refractive index of the material constituting the concave lens attachment layer, the luminous flux collected by the convex microlens is not diffused by the concave lens attachment layer. For this reason, the condensing characteristic can be improved.

In addition, since the concave lens mounting layer provided directly below the support layer is made of a material having a lower refractive index than the support layer, the curvature of the convex microlenses can be made smaller than without the concave lens installation layer without increasing the focal length. . Therefore, reflection of incident light on the convex microlens surface can be prevented.

According to the manufacturing method of the solid-state imaging device of the present invention, the lattice pattern layer is thermally melted to form a concave microlens, and then the concave microlens is etched so that the concave microlens is flat to provide a concave microlens layer. Allow to be transferred to the layer. The solid state imaging device of the present invention is thus manufactured.

According to this method, a solid-state imaging device is formed by thermal melting a lattice pattern layer and forming the lattice pattern layer into a concave microlance layer.

Further, in the above method, an overcoat layer made of transparent resin is formed on the lattice pattern layer, so that the overcoat layer can act as a concave microlens layer. Therefore, the concave microlens layer can be manufactured without thermal melting the lattice pattern layer. For this reason, the concave micro lens layer with good reproducibility can be formed.

As can be seen from the above, since the collimator is installed directly on the photoelectric conversion unit, the solid state imaging device of the present invention can efficiently photoelectrically convert the incident light beams as shown in FIGS. The incident light may be suppressed by the photoelectric conversion unit. In addition, as shown in FIG. 9B, by preventing the incidence of oblique incident light, it is possible to realize the improvement of the overall sensitivity and the suppression of smear at the same time.

In addition, by combining the most convex microlens with the lowest curvature and the concave lens attachment layer having a low refractive index, light reflection on the surface can be suppressed without impairing the light condensing characteristics.

Claims (12)

A plurality of pixels including a photoelectric conversion unit: a convex microlens disposed on the photoelectric conversion unit: a support layer formed between the photoelectric conversion unit and the convex microlens to support the convex microlens: between the support layer and the photoelectric conversion unit 10. A solid-state imaging device comprising a concave microlens layer disposed and formed of a material having a higher refractive index than a material constituting the support layer; and a concave lens attachment layer disposed between the concave microlens layer and the support layer to support the support layer. And the material of the convex microlens, the material of the support layer and the material of the concave microlens layer are all designed to have a higher refractive index than the material of the concave lens mounting layer. A method for manufacturing a solid-state imaging device, which sequentially forms a concave microlens layer, a support layer, and a convex microlens on a photoelectric conversion portion; Forming a layer of a transparent material having a refractive index higher than that of the material constituting the convex microlens and the material constituting the support layer on the photoelectric conversion portion; Forming a lattice resist pattern of a photosensitive resin material having a through hole opposite the photoelectric conversion portion on a surface of the layer of transparent material; Thermally melting the grating resist pattern into a resist layer having a concave microlens shape; And etching the resist layer to transfer the concave microlens shape of the resist layer to the layer of transparent material under the resist layer, thereby converting the layer of transparent material into the concave microlens layer. Method of manufacturing an imaging device. A method for manufacturing a solid-state imaging device, which sequentially forms a concave microlens layer, a support layer, and a convex microlens on a photoelectric conversion portion; Forming a lattice pattern layer on the photoelectric conversion portion formed of a photosensitive resin having a light transmittance and a refractive index higher than a constituent material of the support layer and having a through hole facing the photoelectric conversion portion; And melting the lattice pattern layer to convert the lattice pattern layer into a concave microlens layer. A method for manufacturing a solid-state imaging device, which sequentially forms a concave microlens layer, a support layer, and a convex microlens on a photoelectric conversion portion; Patterning and curing the photosensitive resin material in a lattice shape to form a lattice pattern layer having a through hole facing the photoelectric conversion part on the photoelectric conversion part; and an overcoat layer made of transparent resin on the lattice pattern layer. Forming an overcoating layer to form the concave microlens layer; Solid state imaging device manufacturing method comprising a. The manufacturing method of a solid state imaging device according to claim 2, wherein said etching step is a dry depositing step. 5. The method of manufacturing a solid state imaging device according to claim 4, wherein said overcoating layer made of transparent resin has the same refractive index as that of polystyrene. The method of manufacturing a solid state image pickup device according to claim 4, further comprising the step of adding another overcoating layer made of a resin having a lower refractive index than the concave microlens layer. 5. A method according to claim 4, wherein the formation of the concave microlens layer is controlled by adjusting the line width of the resist pattern of the lattice pattern layer. A method for manufacturing a solid-state imaging device that sequentially forms a concave microlens layer, a support layer, and a convex microlens on the photoelectric conversion portion, the method comprising: forming a concave microlens on the photoelectric conversion portion; Depositing a resist on the concave microlens; Exposing the resist by photolithography to form a lattice pattern surrounding a hole portion facing the photoelectric conversion portion; Curing the resist; And after the curing step, overcoating the resist and the concave microlenses with a resin to form a concave lens attachment layer. 10. The method of manufacturing a solid state imaging device according to claim 9, further comprising providing another overcoating resin layer having a larger refractive index than the resin on the concave lens attachment layer. The method of claim 10, wherein the overcoating resin has the same refractive index as that of polystyrene. 10. The method of claim 9, wherein the resin has a lower refractive index than that of the concave microlens.